Missing SyntaxError check for `async for` in lambda inside an async function

[Juniormin123]

Description and reproduce

pyright, (and pylance in vscode), does not warn against SyntaxError for the following code:

import asyncio
import random
from collections.abc import Callable


async def async_gen(limit: int = 10):
    while True:
        if limit <= 0:
            return
        await asyncio.sleep(rtn := random.random())
        yield rtn
        limit -= 1


async def run_with_callback[U, T](u: U, callback: Callable[[U], T]) -> T:
    await asyncio.sleep(0)  # some async ops
    return callback(u)


async def test_async_for_in_lambda():
    result = await run_with_callback(
        async_gen(5),
        lambda ag: [x async for x in ag],  # <- fails to detect syntax error, raises in runtime
    )
    print(result)


# def run_with_callback_sync[U, T](u: U, callback: Callable[[U], T]) -> T:
#     return callback(u)
# 
# 
# def test_async_for_in_lambda_sync():
#     result = run_with_callback_sync(
#         async_gen(5),
#         lambda ag: [x async for x in ag],  # <- correctly detect syntax error, raises in runtime
#     )
#     print(result)


if __name__ == "__main__":
    asyncio.run(test_async_for_in_lambda())

Runtime output:

 ➜ python /tmp/test.py
  File "/tmp/test.py", line 23
    lambda ag: [x async for x in ag],  # <- fails to detect syntax error, raises in runtime
               ^^^^^^^^^^^^^^^^^^^^^
SyntaxError: asynchronous comprehension outside of an asynchronous function

pyright output:

 ➜ pyright /tmp/test.py
0 errors, 0 warnings, 0 informations

Related versions

• pyright: 1.1.407
• pylance: 2025.10.4
• python: Python 3.14.0, conda distributed
• OS: should be irrelevant, as this is pure Python

Note

May be this can be related to #9414